Dritz-Omnigrid Mat. Omnigrid mats have several unique features that quilters appreciate: One side features a medium green background with bright yellow grid lines and the other side features a solid grey without grid lines. Both sides feature a forgiving surface and will not damage your rotary cutter. The grids on these mats feature inch markings to the 1/8 inch and a full surface grid with 45 degree angles as well. Mat measures 18-3/4x12-3/4 inches with an 12x18 inch grid. WARNING: Contains Phthalates: known to the State of California to cause birth defects and other reproductive harm.